sublimemediumRule

Attachment: HTML smuggling with hex strings

Recursively scans files and archives to detect HTML smuggling using hex-encoded string content.

MITRE ATT&CK

T1566 T1566.001 T1566.002 T1598 T1204.002 T1486 T1036 T1027

defense-evasion

Detection Query

type.inbound
and any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_extension in~ $file_extensions_common_archives
          or .file_type == "html"
        )
        and any(file.explode(.),
                any(.scan.strings.strings,
                    // ["\x00\x00\x00\xAA..."]
                    regex.icontains(., '(\\x([a-zA-Z0-9]{2})){100}')
                )
        )
)

Author

ajpc500

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

References

Raw Content

name: "Attachment: HTML smuggling with hex strings"
description: |
  Recursively scans files and archives to detect HTML smuggling using hex-encoded string content.
references:
  - "https://delivr.to/payloads?id=e86dc61b-6d12-49f2-a298-31a3ce1f0158"
  - "https://app.docguard.io/ad10f40d3b3c6b4961a1c849948e76f513702405a8588d69b6661dbef6253b48/results/dashboard"
authors:
  - twitter: "ajpc500"
type: "rule"
severity: "medium"
source: |
  type.inbound
  and any(attachments,
          (
            .file_extension in~ ("html", "htm", "shtml", "dhtml")
            or .file_extension in~ $file_extensions_common_archives
            or .file_type == "html"
          )
          and any(file.explode(.),
                  any(.scan.strings.strings,
                      // ["\x00\x00\x00\xAA..."]
                      regex.icontains(., '(\\x([a-zA-Z0-9]{2})){100}')
                  )
          )
  )
attack_types:
  - "Credential Phishing"
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "HTML smuggling"
detection_methods:
  - "Archive analysis"
  - "Content analysis"
  - "File analysis"
  - "HTML analysis"
  - "Javascript analysis"
id: "b4208ed6-fdde-5165-a5ca-1fe469c64046"